The Saudi student was arrested after he attempted to purchase over the Internet the chemical phenol, a key ingredient in the explosive trinitrophenol, or TNP, according to an FBI chemist cited in the affidavit.

A North Carolina company alerted federal agents Feb. 1 after Aldawsari tried to buy online 10 bottles of the toxic chemical phenol, which can be used to make the explosive trinitrophenol, also known as TNP, USA TODAY's Kevin Johnson wrote earlier this month when court documents were released.

A saturated solution is prepared by dissolving 140 grains of recrystallized picric acid (carbazotic acid, or, more correctly, trinitrophenol) in 1 pint of water with heat, and decanting the clear solution.

Ten 500-millimeter bottles of 80%-concentration phenol, which can be used to make the explosive trinitrophenol, had been bought for $434.57 on Aldawsari's debit card, and were to have arrived via FedEx.

Aldawsari, investigators allege, bought "concentrated nitric and sulfuric acids" and tried to buy phenol - which "can ... be used to make the explosive trinitrophenol, also known as T.N.P., or picric acid."